Environmental and Safety Aspects of Spent Hydroprocessing Catalysts - Spent Hydroprocessing Catalysts - page 102

Figure 5.1: Schematic of spent catalyst withdrawing system from fixed bed reactor [From ref. 320 .
Reprinted with permission].
cycle, a chemical inhibitor is injected and circulation continues until it is necessary. At about
140 ◦ C, the carrier oil is replaced by N 2 to achieve a drying and further cooling of spent
catalyst. A similar method involves treating spent catalyst (while still in reactor) with a mixture
comprising oxygen-containing hydrocarbons having carbon number of at least 12 [324] .
After unloading, a decision has to be made regarding the fate of the spent catalyst, although
most of the petroleum refineries have already a necessary system in place, usually based on
many years of practical experience. This may include the agreement with a partner, i.e.,
certified company to perform regeneration, metal reclamation, and storage of hazardous waste.
For refiner, the situation can be simplified in the case that the involvement of partner during the
catalyst unloading, packaging, and shipping is part of the agreement. The decision making
process has been described elsewhere [303] . Otherwise, it is responsibility of refiner to take all
necessary precautions during the entire presence of spent catalyst on the refinery site to ensure
safety and environmental acceptance.